This is a Phase 2, open-label, pilot trial of the efficacy and safety of YF476 in the treatment of type II gastric carcinopids and /or ECLcell hyperplasia/dysplasia in patients with ZEs. Thee purpose of this protocol is to assess if YF476 can have a 25% reduction in the size or number of endoscopically visible type II gastric carcinoids; or if it can improve histological grade of gastric carcinoids and/or ECL cell hyperplasia. Other effects being studied are: if YF476 can control and maintain gastric acid production; if it has any effect on serum biomarker (ie; chromogranin level); improvement in reflux/dyspepsia symptoms based on GERD-HRQL; and, if it safe and well tolerated when added to other concomitant medications in ZEs patients. find out whether treatment with YF476 is safe and effective at achieving regression of type II gastric carcinoid tumors, or the abnormal growth of gastric ECL cells, in patients with ZES. Due to the cumbersome number of frequent visits to the NIH, accrual for this protocol has been slow. At this time, three patients are currently enrolled and have tolerated the drug well. Results from these first 3 patients are inconclusive due to the small number enrolled. The following changes have been made to the protocol. Updated animal and human study data has been incorporated. The starting drug dose was updated from 50 mg daily to 100 mg daily with plans for increasing the maximum allowed dose following six subjects safely completing 12 weeks at the 100 mg/day dosing. The third inpatient assessment visit has been removed and only patients who respond to treatment are required to complete the follow-up visit. The inclusion criteria has been clarified so that subjects with type II gastric carcinoids and/or ECL cell hyperplasia/dysplasia may enroll at any point.